Turbochargers are well known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric pressure (boost pressures). A conventional turbocharger essentially comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing connected downstream of an engine outlet manifold. Rotation of the turbine wheel rotates a compressor wheel mounted on the other end of the shaft within a compressor housing. The compressor wheel delivers compressed air to the engine intake manifold.
One known approach to improving turbocharging efficiency and reducing emissions for an engine with a wide speed/load range is to provide a sequential two stage turbocharging system, comprising one relatively small high pressure turbocharger and another relatively large low pressure turbocharger. The turbochargers are arranged in series so that exhaust from the engine flows first through the smaller turbine of the high pressure turbocharger and then through the larger turbine of the low pressure turbocharger. The compressors of the two turbochargers are also arranged in series, with air flowing first through the relatively large compressor of the low pressure turbocharger and then through the relatively small compressor of the high pressure turbocharger. For high altitude large engine operation, air-to-water intercoolers and aftercoolers, which also may be referred to as water-to-air intercoolers and aftercoolers, can be employed to provide cooling of the intake flow after compression by the low pressure and high pressure turbochargers prior to delivery of the intake air to the intake manifold in order to increase efficiency and power output.
One problem with water cooled multi-stage turbocharger systems involves the complexity of the plumbing required to provide water to the intercooler and aftercooler to adequately cool the intake air flow. The plumbing and other peripherals associated with air-to-water intercoolers and aftercoolers hinder access to the engine's V-cavity and other peripheral components, inhibiting serviceability. Furthermore, installation costs are increased due to the complexity of the plumbing required to support air-to-water intercooling, and shipping and packaging costs are increased as well due to the large footprint and profile created by the support frame and other components required to support and operate the air-to-water intercoolers along with the associated plumbing. Therefore, there remains room for further improvements in this technology area.